Eyeglass frame including shape-memory elements

ABSTRACT

Eyeglass frames fabricated from shape-memory alloys which have optimized elasticity properties which exhibit a combination of shape-memory and elastic properties, which utilize the shape-memory property of these alloys in fastening elements, or which utilize the flexibility and fatigue resistance of the martensite state of the alloys as a hinge element are disclosed.

This application is a continuation-in-part of U.S. patent applicationSer. No. 876,077 filed June 19, 1986, now U.S. Pat. No. 4,772,112, whichis in turn a continuation-in-part of U.S. patent application Ser. No.676,823 filed Nov. 30, 1984, now abandoned, which is in turn acontinuation-in-part of U.S. patent application Ser. No. 558,604 filedDec. 6, 1983, now abandoned.

FIELD OF THE INVENTION

The present invention relates to frames for eyeglasses and moreparticularly to frames fabricated from shape-memory alloys.

BACKGROUND OF THE INVENTION

The metals which have historically been used to make metal eyeglassframes have usually been chosen in large part for their ease offabrication. Metals such as nickel-silver, monel, and phosphor bronzehave fairly high yield strength but quite low work-hardening, whichallows them to accept large deformations during manufacture. In use,however, they tend to bend rather suddenly and in quite localizedsections if their yield strength is exceeded. Such sharp bends are verydifficult to removed without leaving "kinks" in the bent section. Thehigher strength frame materials, such as high strength stainless steelsand beryllium-copper, are able to withstand much higher elastic strainswithout permanent deformation. They are still limited to only about 1%elastic strain, however, and if their yield strength is exceeded a bendis formed which is difficult to remove.

A number of references such as U.S. Pat. No. 4,472,035, Japanese PatentPublication No. 57-115517(A) and Japanese Patent JP-084714 havesuggested the use of shape-memory alloys, especially the nickel-titaniumalloys, for use as frame components due to their "superelastic" or"pseudoelastic" properties. Although these terms are often mistakenlyused interchangeably, they refer to two distinctly different propertiesof the alloys. Careful study of all of these references, specificallyU.S. Pat. No. 4,472,035 and Japanese Patent JP-084714, shows that theelastic property cited is the "pseudoelastic" property of shape-memoryalloys. This pseudoelasticity occurs in a limited temperature rangeslightly above the stress-free austenite to martensite transformationtemperature. It involves the creation of stress-induced martensite whichsimultaneously undergoes strain as it forms to relieve the appliedstress. As soon as the applied stress is removed, the thermally unstablemartensite reverts to austenite, and the strain spontaneously returns tozero. This behavior gives a very high apparent elasticity to thematerial without inducing any permanent strain, but is narrowly limitedin the temperature range where it can be utilized in a given alloy.Because the pseudoelasticity depends upon behavior within a narrowportion of the transformation temperature spectrum, lowering thetemperature as little as 10° C. may change the behavior to normalshape-memory. In this case a deformed component will remain deformedunless it is heated. Also, the yield strength of this alloy, if it isannealed to give good pseudoelastic properties, is too low at lowtemperatures to function as a satisfactory component. Conversely, if thepseudoelastic component is heated by as little as 10° C., the amount ofpseudoelastic strain is significantly reduced. At even highertemperatures the pseudoelasticity is eliminated because the stressneeded to stress induce the martensite exceeds the yield strength of theaustenite, and permanent deformation results. Thus, the effective usefultemperature range for purely pseudoelastic components may be as littleas 20° C. This range is too narrow to be of service to eyeglass frameswhich must function in winter days as cold as -20° C. and in hot sunnydays with possible temperatures over 40° C.

Thus, while both the elastic properties and memory properties ofshape-memory alloys have been discussed as potentially useful ineyeglass frames, it is clear that previous workers have not fullyunderstood the limitations on the use of these materials, nor have theyrevealed any information on the proper thermo-mechanical processingnecessary to utilize the alloys as frame components.

SUMMARY OF THE INVENTION

It is the purpose of the instant invention to provide eyeglass frameswhich (1) are highly resistant to permanent deformation, or "kinking",over the full range of ambient temperatures, or (2) are sufficientlyresistant to deformation and are readily restorable to the undeformedshape by heating, or (3) are easily disassembled and reassembled, or (4)do not require screws in the hinges.

To accomplish this purpose there is provided frames having portionsthereof fabricated from shape-memory alloys which (1) have thecombination of superelastic and work-hardened pseudoelastic properties,hereinafter "optimized elasticity" properties, or (2) exhibit acombination of shape-memory and elastic properties, or (3) utilize theshape-memory property of these alloys in fastening elements, or (4)utilize the flexibility and fatigue resistance of the martensite stateof the alloys as a hinge element.

In one aspect of the invention, there is provided an eyeglass framehaving at least a pair of rims and a pair of corresponding temples, andhaving at least a portion thereof fabricated from shape-memory alloywork-hardened at least 30% and having greater than 3% elasticity over atemperature range from -20° C. to +40° C.

In another aspect of the invention, there is provided an eyeglass framehaving at least a pair of rims and a pair of corresponding temples, andhaving at least a portion thereof fabricated from shape-memory alloywork-hardened at least 30%, followed by a heat treatment at atemperature not exceeding 400° C. for not less than one hour, and havinga minimum of 3% heat-recoverable shape-memory, a yield strength greaterthan 30,000 psi (207 MPa [MegaPascal]), and at least 3% elasticity.

In yet another aspect of the invention, there is provided an eyeglassframe having at least one fastener portion, said fastener portion madeof shape-memory alloy with a martensite transformation temperature belowambient temperature, said alloy having an austenite transformationtemperature above which the alloy transforms to its austenite state andin so doing applies a fastening or unfastening force.

Still in yet another aspect of the invention, there is provided aneyeglass frame having a pair of rims and a pair of correspondingtemples, said rims connected to said temples by a pair of hingeportions, said hinge portions made of shape-memory memory alloy with anaustenite transformation temperature above ambient temperature, belowsaid austenite transformation temperature said alloy being in itsmartensite state and being highly flexible and resistant to fatigue.

In another aspect of the invention, there is provided an eyeglass framehaving at least one fastener portion, said fastener portion made ofshape-memory alloy with a martensite transformation temperature aboveambient temperature, said alloy having an austenite transformationtemperature above which the alloy transforms to its austenite state andin so doing applies a fastener force, said alloy maintaining a fasteningforce when said alloy returns to its martensite state.

In yet another aspect of the invention, there is provided an eyeglassframe having at least one fastener portion, said fastener portion madeof shape-memory alloy with a martensite transformation temperature belowambient temperature, said alloy having an austenite transformationtemperature above which the alloy transforms to its austenite state andin so doing applies an unfastening force.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a generic eyeglass frame includingdetail with respect to one embodiment of the invention.

FIG. 2A is a graph of strain versus temperature at a fixed appliedstress. The temperatures which characterize the transformation betweenthe austenite and martensite phases of a shape-memory alloy are definedon the graph.

FIGS. 2B-2E represent the stress-strain behavior of a fully annealedshape-memory alloy at four different temperatures wherein:

FIG. 2B--the temperature T₁ is below M_(s) ;

FIG. 2C--the temperature T₂ lies slightly above M_(s) and well belowM_(d) ;

FIG. 2D--the temperature T₃ is higher than T₂ but still below M_(d) ;

FIG. 2E--the temperature T₄ is greater than A_(f) and greater than M_(d);

FIG. 2F represents the stress-strain behavior of a martensite alloy atT<M_(s), such as shown in FIG. 2B, which alloy has been work-hardened.This is the behavior defined as superelastic;

FIG. 2G shows a combination of elastic and shape-memory properties atT<M_(s) for an alloy, such as shown in FIG. 2B, which has beenwork-hardened and partially annealed; and

FIG. 2H shows the stress-strain behavior of a martensite alloy at M_(s)<T<M_(d), such as shown in FIG. 2C, which alloy has been work-hardened.This behavior is defined as "optimized elasticity".

FIG. 3 is a cross-sectional view taken along section lines 3--3 in FIG.1 of a lens-retaining rim to apply a fastening force with two-way actionactivated by heat.

FIG. 4 is a cross-sectional view similar to FIG. 3 of an alternateembodiment.

FIG. 5 is a partial cross-sectional view of an eyeglass frame templepivotally coupled to a rim by a fastener portion.

FIGS. 6, 7, 9 and 10 are exploded partial perspective views of variousembodiments of shape-memory alloy fasteners employable in coupling atemple to a rim as in FIG. 5.

FIG. 8 is a perspective view of the fastener of FIG. 7 in the openedconfiguration.

FIG. 11 is a partial cross-sectional view of a fastener employable inthe embodiment of FIG. 10.

FIG. 12 is a partial perspective view of a fastening arrangementemploying a shape-memory nut and/or bolt.

FIGS. 13 and 14 are the front view and a partial cross-sectional sideview, respectively, showing the coupling of the nose bridge and templesto the lenses of the eyeglasses. FIG. 14 illustrates an alternate lensinterface.

FIG. 15 is a perspective view of a shape-memory alloy rim which bothengages a lens and pivotally engages a temple upon heat recovery.

FIG. 16 is a partial perspective view of a support for a nose pad foruse in the present invention.

FIG. 17 is a partial perspective view of a one-piece hinge in accordancewith the present invention.

FIG. 18 is a cross-sectional view of a temple employed in the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, eyeglasses shown generally at 10 are shown having aframe 12. The frame 12 includes two eyeglass rims 14 and 16, a nosebridge 18, nose pads 19 and 21, and temples 20 and 22 which are hingedto the rims 14 and 16, respectively. The temples 20 and 22 extend backover the ears of the wearer (not shown), the bridge 18 joins the twolenses, and the nose pads, which rest on the nose of the wearer, areattached to the rims by wires 23 and 25.

FIGS. 2A through 2F represent stress-strain graphs of a typicalshape-memory alloy under different conditions. The temperature T is thetemperature at which the stress-strain test are conducted and isgenerally also within the temperature range in which the alloy is to beused.

The mechanical properties of shape-memory alloys are very dependent uponprocessing and temperature, particularly in the temperature range nearthe transformation temperatures depicted in FIG. 2A.

To characterize the mechanical properties of frame components, theuniaxial tensile properties will be cited because they are the mosteasily tested and compared to other materials or other results. To testthe frame components in question, the straight blade of the temples withuniform cross-section were pulled in a standard testing machine whilestrain was measured using an extensometer fastened to the actual testsection under study and the load was measured by the testing machine.

In FIG. 2A the strain E that the alloy undergoes when subjected to afixed stress U is plotted as a function of temperature. Upon cooling,there is a sudden increase in strain when the alloy reaches themartensite start transformation temperature, M_(s), at which temperaturethe high temperature structure austenite microstructure begins totransform into the much softer low temperature martensitemicrostructure. The increase in strain continues until the alloy iscompletely converted into martensite at the martensite finishtemperature, M_(f). When the alloy is reheated the transformation backto austenite begins at the austenite start temperature, A_(s), and iscompleted at austenite finish temperature, A_(f). Generally, A_(s) issomewhat higher than M_(f), and the curve of the temperature differencebetween the cooling and heating is called hysteresis. The width of thehysteresis can be 10° C. to 100° C. in nickel titanium alloys and evenwider in some copper-based alloys.

It has been found, however, that when the alloy is subjected towork-hardening of at least about 30%, preferably at least about 40%,plastic deformation, a different set of stress-strain curves isobtained, and specific components of an eyeglass frame can be madeutilizing an alloy having an appropriate temperature range (T), plussuch work-hardening (and, in some cases, subsequent annealing) toachieve desired properties. For example, substantial work-hardening of ashape-memory alloy (that is, about 30% or more plastic deformation)results in a highly springy "pure superelastic" behavior at T<M_(s), asshown in FIG. 2F. This figure should be contrasted with FIG. 2B whichshows the same alloy without work-hardening. At M_(s) <T₂ <M_(d) thesame alloy will behave as shown in FIG. 2H where it is described as"work-hardened pseudoelastic." FIGS. 2F and 2H represent the idealcharacteristics for use in purely elastic eyeglass components, e.g.,temples bridges, and nose pad support wires. Whereas the pseudoelasticbehavior in FIG. 2C is too limited in temperature range to be useful,the behavior in FIG. 2F or FIG. 2H can be achieved throughout the range-20° C. to +40 ° C. by selecting an alloy with an appropriate M_(s)temperature and processing the alloy to achieve optimum work-hardening.Should the alloy be exposed to temperatures above M_(s), thework-hardened pseudoelastic behavior of the alloy, as shown in FIG. 2H,ensures that it retains the desired elasticity and strength.

By carefully working-hardening the frame material to the appropriatelevel and then retaining this work-hardening after all other processingby not performing any anneals, it is possible to obtain an extremely"springy" component whose yield strength is acceptably high at allrelevant temperatures. At temperatures below the materials's M_(s)temperature, the work-hardened structure will not undergo easyheat-recoverable strain as shown in FIG. 2B, but rather exhibits thebehavior shown in FIG. 2F. If the service temperature should fallbetween M_(s) and M_(d) for the alloy, the extreme springiness due tothe pseudoelastic effect is partially retained while the resistance topermanent deformation of either the martensite or austenite phases dueto the work-hardening is utilized (FIG. 2H). In all of these situations,the low effective modulus of the material and the enhanced yieldstrength due to the correct retained work-hardening make possiblecomponents with an elasticity many times that of standard framematerials.

To achieve the desired very high elasticity property throughout thetemperature range for eyeglass frame usage (i.e., about -20° C. to +40°C.), it is desirable to combine aspects of both pseudoelasticity andsuperelasticity in the components. (See FIGS. 2C and 2F.) This isachieved by choosing an alloy whose pseudoelastic temperature rangematches the upper portion of the desired service temperature range(i.e., from about 10° C. to 40° C.) and applying work-hardening toachieve satisfactory superelastic behavior in the lower portion of theservice temperature range. By applying work-hardening of at least about30% to the component, plastic and heat-recoverable strains in themartensite phase, up to a stress of at least 75 ksi (517 MPa), aresuppressed. In the pseudoelastic temperature region, the properties thenbecome a combination of superelastic and pseudoelastic, i.e., "optimizedelasticity" properties (see FIG. 2H) up to stresses of at least 75 ksi(517 MPa). Thus, throughout the temperature region of interest foreyeglass frames, the component acts completely elastically up to strainsof 6% or more. This is many times the range achieved with traditionalmetal frame materials.

For example, a suitable component can be made using a shape-memory alloyhaving a transformation temperature of 0° C. Swaging a temple section to0.060" (1.52 mm) diameter, annealing the section at 600° C. for 15minutes, and then pressing that section to a flattened section of 0.036"(0.92 mm)×0.083" (2.11 mm) (plastic deformation of greater than 45%)will impart sufficient cold work. Said component will support a stressof over 150 ksi (1,033 MPa) at 4% tensile strain and show completeelastic spring back at room temperature. It is understood that alternateways of imparting equivalent amounts of cold work, such as by anadditional swaging step, or by rolling or pressing to other shapes, willresult in similar strength and elasticity properties.

From the above, it can be seen that an eyeglass frame may be constructedwith portions thereof exhibiting optimized elasticity, such portionsbeing made from shape-memory alloy work-hardened at least about 30%,preferably at least about 40%, and having greater than 6% elasticityover a temperature range from -20° C. to +40° C.

To utilize the shape-memory feature, especially in such components astemples, it is necessary to achieve a fairly high effective yieldstrength (not less than about 30 ksi [207 MPa]) while still retainingsharp, complete shape-memory recovery from deformations as large as 6%outer fiber strain. Work-hardening and partial annealing resulting analloy which, below M_(s), has a combination of higher yield strength,very springy elastic behavior, and some shape-memory characteristic.This behavior is shown in FIG. 2G. This is accomplished by a finalforming step of the component that applies at least about 30% plasticdeformation and results in a yield strength of at least 75 ksi (517 MPa)in the component, followed by final heat treatment to reduce the yieldstrength from the work-hardened value of at least 75 ksi (517 MPa) to aheat-treated level of 30 ksi (207 MPa) to 50 ksi (344 MPa). Thissequence gives a fully recoverable strain potential of at least 6%.Optimum processing employs a final shaping operation which impartsapproximately 35-40% cold work, followed by a heat treatment above roomtemperature but below 400° C. (e.g., about 275° C.) for over one hour,which reduces the yield strength to 30 to 50 ksi (207 to 344 MPa).

By way of example, a temple component may be made by swaging thematerial to 0.070" (1.78 mm) diameter and annealing at 600° C. for 15minutes. The component is then pressed to a flattened cross-section of0.0875" (2.22 mm) wide×0.049" (1.25 mm) thick (a plastic deformation ofover 35%). The component at this point has a yield strength of over 99ksi (682 MPa). The component is then annealed at 280° C. for five hours.The resulting component has a tensile yield strength of 31 ksi (214 MPa)and a tensile strength of 125 ksi (861 MPa) at 7.5% strain; uponunloading the component gives 3.7% elastic spring back and imparts 3.8%shape-memory recovery when heated.

As another example, to obtain a "stiffer" temple, a component may beswaged to 0.075" (1.91 mm) diameter and then pressed to 0.097" (2.46mm)×0.049" (1.25 mm) (over 38% plastic deformation) after annealing at400° C. for 30 minutes. A final anneal of 250° C. for eight hours givesa component with a yield strength of about 49 ksi (338 MPa) (compared toabout 110 ksi [758 MPa] prior to the anneal) and a tensile strength of113 ksi (778 MPa) at 7.25% strain; when heated the component gives 5.0%elastic spring back and imparts 2.25% shape-memory recovery. It isunderstood that alternate ways of imparting equivalent amounts of coldwork, such as by an additional swaging step, or by rolling or pressingto other shapes, will result in similar strength, shape-memory recovery,and elasticity properties.

From the above, it can be seen that an eyeglass frame may be fabricatedhaving portions thereof made from shape-memory alloy, such portionshaving a minimum of 3% heat-recoverable shape-memory, a yield strengthgreater than 30 ksi (207 MPa), and at least 3% elasticity.

For components in which one uses the shape-memory properties toaccomplish fastening or clamping functions, material as described inFIGS. 2B or 2G may be used. The transformation temperature of thematerial may be chosen to allow cooling to obtain the martensitestructure, and reversion to austenite would occur upon warming toservice temperature; alternatively, the material would require heatingabove the service temperature to cause transformation to austenite,triggering the shape-memory effect. In service the components might beeither austenite or martensite.

From the above it can be seen that an eyeglass frame may be fabricatedhaving at least one fastener portion made of shape-memory alloy with amartensite transformation temperature below ambient temperature, saidalloy having an austenite transformation temperature above which thealloy transforms to its austenite state, and in so doing applies afastening force. The alloy may alternatively have a martensitetransformation temperature above ambient temperature, so that raisingthe alloy to its austenite state will cause the alloy to apply afastening force, said fastening force being maintained when thecomponent is cooled to its martensite state.

In components which utilize the flexible fatigue resistant properties ofthe shape-memory alloys, such as in FIG. 17, the preferred material isthe form described in FIG. 2B. The transformation temperature of thealloy should be above the service temperature range to ensure that thecomponent is always martensite in service and therefore has a lowmartensite yield strength and large, reversible martensite strain. It isalso possible, if the component desirably has a higher effectivestiffness, to use the alloy in the form described in FIGS. 2F, 2G or 2H.

From the above it can be seen that an eyeglass frame may be fabricatedhaving a hinge portion made from shape-memory alloy with an austenitetransformation temperature above ambient temperature, below saidaustenite transformation temperature the alloy being in its martensitestate and being highly flexible and resistant to fatigue.

The above-described shape-memory alloys are applied but not limited toportions of the eyeglass frame, as follows:

    ______________________________________                                        (1)     Optimized elasticity  temples                                                                       wires                                                                         bridge                                          (2)     Elastic & memory      temples                                                                       wires                                                                         rims                                                                          bridge                                          (3)     Fasteners (shape-memory only)                                                                       hinges                                                                        wires                                                                         rims                                            (4)     Martensite            hinges                                          ______________________________________                                    

One alloy of the type that may be used to fabricate the above portionsof the eyeglass frame is the subject of U.S. Pat. No. 3,351,463, whichis incorporated herein by reference. Other literature describing theprocessing and characteristics of suitable compositions includes anarticle by Dr. William J. Buehler, the principal developer of 55nitinol, and William B. Cross entitled "55-Nitinol--Unique Wire Alloywith a Memory," which appeared in the June 1969issue of Wire Journal. Adescription of the materials and certain of the properties may also befound in the brochure entitled "Nitinol Characterization Studies" datedSeptember 1969. This document, identified as N-69-36367, or NASACR-1433, is available from the Clearinghouse for Scientific andTechnical Information, Springfield, VA 22151. All of these publicationsare incorporated herein by reference.

Examples of shape-memory alloys are disclosed in U.S. Pat. Nos.3,174,851 and 3,672,879, incorporated herein by reference. Atitanium-nickel-cobalt alloy is disclosed in U.S. Pat. No. 3,558,369.Suitable binary nickel-titanium shape-memory alloys are well-known tothose skilled in the art and, for example, are described in the patentsand article of Buehler et al, mentioned above.

In FIG. 1, the rim 14 is shown in a contracted shape (recovered state)wherein the rim 14 abuts a lens 24 and forms a tight fit therewith. Rim16 depicts an expandable shape (deformed state) rim relative to a lens26, said rim accommodating the insertion of such a lens. In thisembodiment the rims 14 and 16 apply a fastening force to the lenses.

The rims 14 and 16 are made of shape-memory alloy material such as, butnot limited to, a nickel-titanium alloy, various aluminum brasses,copper alloys, and other known alloys that exhibit shape-memory effect.One well-known nickel-titanium alloy is known as nitinol. In thisfigure, by way of example, the shape-memory alloys may be formed to havea memory configuration to which they return when sufficient heat isgenerated therein. That is, the shape-memory alloy can be deformed andthereafter returns to its memory configuration when it is heated. Thismemory characteristic is attributed to changes of state in the metal oralloy from that of a deformed martensite state to a recovered austenitestate in response to the application of heat. The rims 14 and 16 can bedeformed while the alloy is in its martensite state and thereafterrecovered to a memory configuration, i.e., to their recovered austenitestate, thereby applying a fastening force by exposing the rims 14 and 16to an appropriate temperature. The transition temperatures forshape-memory materials are known in the arts relating to shape-memoryalloys. The methods in which the rims 14 and 16 are directed to atransition, or recovery, temperature include: adjusting the temperatureof the environment surrounding the rims 14 and 16; passing currentthrough rims 14 and 15 to generate heat due to the resistance of thematerial; using inductive heating; or by using other temperature controltechniques. Preferably, a technique which permits close control of thetemperature of the rims 14 and 16 is employed, e.g., dipping the rims inwater of proper temperature.

In one mode of operation, the rims are in the recovered austenite statewhen the lenses are in final position. Rim 14 is shown in memoryconfiguration (recovered) in FIG. 1. In the deformed state, as seen withrespect to rim 16, the rim is sufficiently large to enable the lens 24to be inserted therein. Upon heating, the rim 16 will contract intotight contact with the lens 24, exerting a fastening force. Therefore,in this mode the rim is heated to close upon the lens to retain thelens.

The speed at which the rim 16 contracts may be closely controlled bycontrolling the application of heat to the rim 16. (This feature, it isnoted, pertains to all of the embodiments of the invention as relate torecovery of the metals.)

In another mode of operation, the rim 14 may be in the deformedmartensite state when closed and in tight contact with the lens. Byheating the rim 14 in this mode, the rim in its deformed martensitestate is recovered to its open and recovered austenite state enabling itto apply an unfastening force. Hence, in this mode, insertion andremoval of a lens is performed when the rim is in the memoryconfiguration corresponding to rim 16, and the lens is held in place bya deformed rim corresponding to rim 14.

Referring now to FIG. 3, a preferred cross-section for a rim 30according to the invention is shown. The cross-section is C-shapeddefining a channel 32 along the length of the rim 30. The channel 32 hasa radial dimension which can be selectively increased or decreased toenable release of a lens 34, or retention of the lens 34, respectively.As previously suggested, either release (unfastening) or retention(fastening) can be effectuated by recovery to the memory configuration,the complementary operation being performed by deforming the radialdimension of the rim 30. Deformation of the shape-memory alloycomprising the rim while the alloy is in its martensite state may, ifdesired, be effected by compressing the channel radially inwardly toreduce the channel radius, the channel width being increased uponheating the alloy to the austenite state recovery temperature.

In considering FIG. 3, it should be noted that the lens 34 may beretrained (a) solely or primarily by the ridges 36 and 38 of the rim 30,or (b) by the ridge 36 and 38 together with a friction fit against theinner surface 40 of the rim 30.

As shown in FIG. 3, the rim 30 comprises an inner layer 42 and an outerlayer 44. The inner layer 42 is shown having the ridges 36 and 38disposed therealong. It is also within the scope of the invention toprovide retaining ridges along the outer layer 44. In this latterembodiment, the C-shaped circumference of the outer layer 44 would berelatively greater than the circumference of the inner layer 43.Similarly, engaging the lens 34 by both layers 42 and 44 is alsocontemplated. In any of the above embodiments either the inner layer 42or the outer layer 44 may be fabricated from a shape-memory alloy,depending upon whether the shape-memory alloy is being used to open orto close the C-shaped channel, as will become apparent from thefollowing discussion. The other layer is then preferably stainless steelor some other relatively spring-like metal. When the outer layer 44 isshape-memory alloy, the rim 34 preferably closes upon heating to engagethe lens 34. When the inner layer 42 is shape-memory alloy, the rim 30opens to disengage the lens 34 upon heating to the memory (recovered)configuration. Accordingly, by dipping rim 30 into hot water, the weareror practitioner is able to remove and replace the lens 34, which lenswas engaged upon cooling. It should be recognized that the C-shapedcross-section may be provided in a closed rim (e.g., see FIG. 1) orpartial rim embodiment.

The rim may comprise just a single layer of shape-memory material, asseen FIG. 4, if desired. FIG. 4 also illustrates in cross-section lens50 having grooves 52 and 54 formed on opposite sides of the lens aboutits periphery. A C-shaped frame member 56 is disposed about theperiphery of the lens and has terminal ends 58 and 60 seated in thegrooves 52 and 54, respectively. In this embodiment the shape-memoryalloy frame member 56 applies a fastening force when the alloy is in theaustenite state.

A two-piece rim, such as illustrated in FIG. 3, may be employed, butpreferably a single-piece rim of shape-memory alloy is employed.Elasticity is not a major factor in such an application, but strengthis, and the grooves permit a secure hold on the lens.

It should be realized that the C-shaped cross-section of the rim 56 neednot be circular as illustrated, but may be an alternate shape, e.g.,U-shaped which alternate shape would function similarly. It is alsowithin the scope of the invention to have the rims expand and contractcircumferentially. In FIG. 1 the rim 16 is shown to be circumferentiallyexpanded with respect to rim 14.

Referring now to FIG. 5, the fastening of an eyeglass frame temple 70 toan eyeglass frame rim 72 with a fastener portion, shown generally at 74,is detailed. The fastener portion 74 comprises a shape-memory alloymember 76 having a U-shaped cross-section which extends from the rim 72.Positioned within the U-shaped portion of member 76 is the end portion78 of the temple 70. Pin 80 enables the temple 70 and the member 76 tobe pivotably coupled when the member 76 is closed in the U-shape, asshown in FIG. 5. The member 76 is shown in its memory configuration,i.e., when the alloy is in its recovered austenite state. It isunderstood that the member 76 will remain in this memory configurationeven if it is cooled to its martensite state and may function in thatcondition. The member 76 may be deformed by spreading arms whichcomprise the U-shape apart from each other in said member's deformablemartensite state, which, depending upon the specific alloy and thetransformation temperature, may be at a cold temperature. Below thetransition temperature the temple 70 is thus uncoupled from the member76. The temple 70 can be pivotally re-coupled by the member 76 when thealloy of the member 76 is in its recovered austenite state. In such anembodiment, a shape-memory member is employed and recovered to theinitial position by heat which may be room temperature.

In FIG. 6, a dual open-ended fastener is shown generally at 90 having anH-shaped cross-section. Pins 92 are located at each end of the fastener90. At least one end 96 of the fastener 90 is deformable to open thespace between the arms of that end of the H-shaped cross-section, andthat end is recoverable by heating to a transition recovery temperature.Fastener 90 may be used in an application, such as that shown in FIG. 5,to connect a temple 70 and an eyeglass frame rim (not shown).

The operation of the fastener 90 of FIG. 6 is similar to that of asingle open-ended fastener shown generally at 100 in FIGS. 7 and 8. InFIG. 7, the single, open-ended shape-memory fastener 100 is shownclosed, adjacent temple end portion 102. Pin-like portion 104 is capableof extending through an aperture 106 in the temple end portion 102,thereby forming a pivotal coupling. In FIG. 8, the fastener 100 is opento permit the insertion or removal of a temple end portion.

The scope of the invention is not limited to a single pin such as pin04, but also included is the concept of two half pins (not shown), onehalf which may extend from each arm of the U-shaped fastener 100 toengage an aperture such as 106 in temple portion 102. Also, bothmembers, the temple and frame member, may be yokes with opposed pins, orhemispheres, engaging opposed holes in the other member.

FIG. 9 illustrates another type of fastener shown generally at 110.Rather than having a pin 104 as in FIG. 7, temple end portion 112 hastwo half pins 114 extending therefrom which are receivable incomplementary openings 116 in U-shaped member 110. As in the embodimentsof FIGS. 7 and 8, member 110 made of shape-memory alloy can similarlyopen and close to provide a pivotal coupling.

In FIG. 10 a pivotal coupling is achieved by means of a stud or screwmade from shape-memory alloy. The screw 120 is twisted, or in the caseof a stud is pushed, easily into complementary apertures in a temple endportion 122 and a non-shape-memory U-shaped element 124 when aligned.When recovered, the screw or stud 120 expands to tightly engage theU-shaped element 124. It is understood that element 124 may be aseparate element, as shown, or may be a portion of the rim such asmember 76, shown in FIG. 5.

If the element 120 is a stud, it may take the form of the stud of FIG.11. The stud 120 has a head portion 126 seated in a recess 128 in themember shown generally at 122. A split shank 129 extends from head 126through a hole 130 in a member, shown generally at 124, and throughaligned hole 132 in the end member, shown generally at 122 of thetemple. The end of the stud 120 has a short outwardly extending lip 134which catches on the surface of a shoulder 136 in the bottom leg of theU-shaped member 124.

When it is in its deformed martensite state, the member 120 which isradially compressed slips readily through the aligned holes in thetemple 122 and U-shaped member 124. When expanded, the lip 134 locksinto the recess 136 and also engages the side walls of the temple andlower U-shaped member to lock the members together.

In FIG. 12, a fastener in the form of a bolt and nut assembly is showngenerally at 140 to provide fastening for a lens 142 to an eyeglass rimor other member. As shown therein, the bolt 144 extends through a rim146 and the lens 142 and engages a complementary nut 148. The bolt 144and/or the nut 148 are made from shape-memory alloy material. When thebolt 144 is made of shape-memory alloy, it is preferably deformed bybeing axially elongated, and therefore radially compressed, in itsmartensite state prior to being inserted into the nut 148. When the nutis made of shape-memory alloy, it is preferably deformed by beingexpanded radially before the bolt 144 is inserted therein. Whenrecovered the shape-memory alloy bolt 144 contracts longitudinally andexpands radially. The shape-memory alloy nut 148 contracts radially toeffect tight coupling therebetween. The magnitude of contraction and/orexpansion is readily controlled by the predefined memory configurationof the bolt 144 and/or nut 148. These elements may also be recessed.

An alternative for securing a lens to a rim is illustrated in FIGS. 13and 14 wherein relatively small arcuate rim members are provided whichclamp each individual lens at the temples and at the nose piece.Specifically, shape-memory members 150 and 152 are preferably square andC-shaped in cross-section and arcuate to conform to the circumferentialcurvation of lenses 154 and 156, respectively. Members 150 and 152 maybe integral with the entire bridge of the eyeglasses. The lenses arepreferably grooved, as noted, with respect to the embodiment of FIG. 4to mate with the ends of the C-shaped members.

Referring again to FIG. 13, temples 158 and 160 are secured via hinges162 and 164, to the lens 154 and 156, by members 166 and 168 which aresubstantially identical to members 150 and 152, except for the hingepieces. The method of connection to the lens is also identical. Notemple nor nose pads and wires are shown, but they are considered to bewithin the scope of the invention. The various members 150, 152, 166 and168 are greatly enlarged in the drawings for purposes of clarity ofillustration, but in reality provide a substantially rimless eyeless ofsturdy construction, yet with the ability to readily replace defectiveparts. FIG. 14 illustrates in cross-section an alternative to groovingthe lens wherein a lens such as lens 154 is cut away on each sidethereof at the edge of the lens to accommodate gripping by shape-memoryalloy element 150.

FIG. 15 shows an eyeglass frame generally at 170 having shape-memoryrims 172 and 174 which contract radially inwardly in cantilever fashionat the far ends thereof when heated to a recovery temperature. As therims 172 and 174 decrease in radius upon recovery, lenses 176 and 178inserted therein are engaged by the rims 172 and 174, and temples 180and 182 are pivotally engaged. Specifically, protrusions 184, 186, 188and 190 enter depressions or holes in the temples 180 and 182,respectively.

Further in regard to FIG. 15, it is noted that the temples 180 and 182may be made from shape-memory alloy, stainless steel, or some othermetal when coupled to the rims 172 and 174 with a hinged joint as shown.

Alternatively, the joint may comprise a thin section of shape-memoryalloy such as nitinol which has good flexibility and fatigue properties.That is, instead of using a multi-piece hinge, pivotal coupling may beachieved by using a foldable length of shape-memory alloy 201 disposedbetween each rim 172, 174 and temples 186, 182, respectively, asillustrated in FIG. 17. Piece 201 is made of shape-memory alloy with anaustenite transformation temperature above ambient temperature whereinbelow said austenite transformation temperature (i.e., ambienttemperatures to which the eyeglasses are exposed in use) the alloy is inits martensite state and is therefore highly flexible and resistant tofatigue.

Turning now to FIG. 16, nose rest 21 is shown coupled to a rim 16 by anose pad wire 25 which is connected to rim 16. Nose pad 21 may betightly coupled to nose pad wire 25 by a shape-memory alloy fastener 27.The fastener 27 is deformable in its martensite state from theconfiguration shown to enable the fastener to be inserted or removed.When recovered to its austenite state, the fastener 27 encompasses andengages the pad 27. More importantly, the wire 25 may, like the temples20 and 22 and the bridge 18 shown in FIG. 1, be made of shape-memoryalloy which is resistant to permanent deformation or kinking over thefull range of ambient temperatures. The wires may alternatively beformed from shape-memory alloy which is sufficiently resistant todeformation end which is readily restorable to its undeformed shape byheating.

Referring more specifically to FIG. 17, there is illustrated a hinge forthe temple frame connection. In this modification, both the end 200 ofthe temples 202 and an extension 204 from frame 206 have deep recesses208 and 210, respectively, to accommodate piece 201. The hinge piece 201could also be riveted to the frame and temple. The temples may alsoadvantageously employ shape-memory alloy as previously described.

Referring now specifically to FIG. 18, a cross-section of a temple showngenerally at 212 comprises a U-shaped member 214 of shape-memory alloyfilled with a stiffening insert 216. For extra strength the shape-memoryalloy member could be an I-beam or could have an optional outwarddecorative ridge, such as ridge 218 (illustrated in phantom line). Ifsuch configuration is employed, the channel could be eliminated and thewhole temple covered in plastic. Further, the channel 214 could havereturn legs which close about a stainless steel or similar stiffeninginsert to form an elastic member having memory. The insert 216 may thusbe a thin blade of material which adds strength to the structure butwhich is not strong enough to defeat the memory effect of the memorymaterial.

Other improvements, modifications and embodiments will become apparentto one of ordinary skill in the art upon review of this disclosure. Suchimprovements, modifications and embodiments are considered to be withinthe scope of this invention as defined by the following claims.

What is claimed is:
 1. An eyeglass frame having at least a portionthereof fabricated from nickel-titanium based shape-memory alloy, saidportion being in the work-hardened pseudoelastic metallurgical state,said portion having been subjected to work-hardening and having a loweffective elastic modulus giving a soft, springy feel, said portionhaving greater than 3% elasticity over a temperature range from -20° C.to +40° C.
 2. An eyeglass frame as in claim 1 wherein said frameincludes a pair of temples, said portion comprising said temples.
 3. Aneyeglass frame as in claim 1 wherein said frame includes a bridge, saidportion comprising said bridge.
 4. An eyeglass frame as in claim 1wherein said eyeglass frame includes a pair of lens rims and a pair ofnose pads, each nose pad connected to a respective rim by a nose padwire, said portions comprising said nose pad wires.
 5. An eyeglass framehaving at least a portion thereof fabricated from nickel-titanium basedshape-memory alloy, said portion being in the work-hardened andheat-treated condition, said portion having been subjected to at least30% work-hardening followed by a heat-treatment at a temperature notexceeding 400° C. for not less than one hour and having a minimum of 3%heat-recoverable shape-memory, a yield strength greater than 30,000 psiand at least 3% elasticity.
 6. An eyeglass frame as in claim 5 whereinsaid frame includes a pair of temples, said portions comprising saidtemples.
 7. An eyeglass frame as in claim 5 wherein said frame includesa bridge, said portion comprising said bridge.
 8. An eyeglass frame asin claim 5 wherein said eyeglass frame includes a pair of lens rims anda pair of nose pads, each nose pad connected to a respective rim by anose pad wire, said portions comprising said nose pad wires.